Global Patent Index - EP 0171121 A3

EP 0171121 A3 19880907 - DATA INPUT KEYBOARD WITH GALVANIC CONTACTING KEYS

Title (en)

DATA INPUT KEYBOARD WITH GALVANIC CONTACTING KEYS

Publication

EP 0171121 A3 19880907 (DE)

Application

EP 85201253 A 19850730

Priority

DE 3429309 A 19840809

Abstract (en)

[origin: US4709228A] In matrix keyboards whose keys are provided with conductive contacts and are arranged at respective crosspoints of conductors, a diode is connected in series with each key contact in order to allow for n-key rollover, i.e. the simultaneous actuation of several keys in an arbitrary configuration. For many technical realizations of the key contacts, for example in the form of electrically conductive materials provided on plastics foils by silkscreening, the series connection of a diode with each contact element is not simply possible. In accordance with the invention it is proposed to connect an ohmic resistor, which can also be provided by means of a silkscreening process, in series with each key contact and to connect the interrogated matrix conductors to a point of low impedance. Thus, current control is used to a high degree in order to ensure that no signal voltage which is capable of exerting an effect via other actuated keys can appear on the interrogated conductor. The point of low impedance is effectively formed by the inverting input of an operational amplifier which is fed back by means of a resistor.

IPC 1-7

H03M 11/00

IPC 8 full level

G06F 3/02 (2006.01); H03M 11/00 (2006.01)

CPC (source: EP US)

H03M 11/003 (2013.01 - EP US)

Citation (search report)

Designated contracting state (EPC)

DE FR GB IT SE

DOCDB simple family (publication)

EP 0171121 A2 19860212; EP 0171121 A3 19880907; DE 3429309 A1 19860220; JP S6148022 A 19860308; US 4709228 A 19871124

DOCDB simple family (application)

EP 85201253 A 19850730; DE 3429309 A 19840809; JP 17438585 A 19850809; US 72078785 A 19850408